The present invention relates to a tap assembly for a liquid vessel, especially for a cylinder for pressurized liquefied gas, having an overfill protection device (OPD) to prevent overfilling of the vessel or gas cylinder, as well as a float controlled level gauge for detecting and indicating the level of the fluid or liquefied gas remaining in the vessel or gas cylinder.
A tap for a gas cylinder having an overfill protection device is disclosed for example in U.S. Pat. No. 5,487,404 issued on Jan. 30, 1996 to Leon Kerger and also in U.S. Pat. No. 6,640,829 issued on Nov. 4, 2003 to Loll Kerger, both of which are incorporated herein by reference. Mounted below the body of the gas tap is an overfill protection device (OPD) having a valve element movable into an open position by the liquefied gas to be filled into the gas cylinder and a pivotably mounted float effecting closing of the valve element when the liquefied gas reaches a predetermined maximum level within the gas cylinder.
A gas tap having a capacitive level gauge for detecting and indicating the level of the liquefied gas within a gas cylinder is disclosed, for example, in U.S. Pat. No. 5,701,932 issued on Dec. 30, 1997 to George Burscheid et al. A capacitive level gauge is also disclosed in U.S. Pat. No. 4,730,489 issued on Mar. 15, 1988 to Linze Hoekstra. In co-pending and co-owned U.S. patent application Ser. No. 11/000,655 filed Dec. 1, 2004 to Jean-Claude Schmitz and Linze Hoekstra, which is incorporated herein by reference, there is disclosed a gas valve assembly having an overfill protection device and a capacitive level gauge having lamellar electrodes disposed closely adjacent the OPD for insertion with the OPD through a small diameter opening into a gas cylinder. The known capacitive level sensors are electrical level sensors requiring an electrical power source, such as a battery, which must be replaced from time to time, to ensure operation of the level gauge.
International Application WO 00/02015 discloses a level gauge having a magnetically driven level indicating device. This level gauge has a pivotably mounted float coupled through a gear system to an elongate rod to rotate the rod about its longitudinal axis. The rod carries in a head portion of the gauge a permanent magnet. Rotation of said permanent magnet with said rod actuates a pointer of the indicating device by magnetic force. This known level gauge is not appropriate for use with a tap provided with an overfill protection device. The overfill protection device is dimensioned to fit snuggly through an opening of the vessel and if a level gauge of the type disclosed in WO 00/02015 is added to the assembly of the overfill protection device, the level gauge would no longer be insertable through the vessel opening, unless the diameter of the opening is increased, which is undesirable. Of course, a second opening could be formed in the vessel for a separate level gauge, but providing a second opening in the vessel is also undesirable.
Reference is also made to U.S. Pat. No. 5,479,820 issued on Jan. 2, 1999 to Nicolas M. G. Fekete, which discloses a cryogenic gauge provided with a magnetically actuatable level indicator and having an axially movable stem on which an axially movable float is mounted. The stem carries a magnet at an upper end thereof received within a gauge head. This US patent merely concerns a level gauge but does not relate to a tap for a liquid vessel provided with an overfill protection device.